The present invention relates to plunger actuated switches and particularly switches of this type which are actuated by user movement of an operating member which contacts the plunger of the switch. In applications of this sort, the plunger actuated switch must be installed or mounted proximate the operating member moved by the user such that the operating member is properly positioned to contact the plunger and effect switch actuation in a desired point in time or position relative to the movement of the operating member by the user. In order to accomplish this, the switch mounting must be adjustable so as to position the at-rest position of the switch plunger properly with respect to the at-rest position of the operating member to be moved by the user.
A particular application of a plunger actuated switch is that encountered in automotive stop lamp switches where the switch is mounted in the vehicle and initially positioned with respect to the at-rest position of the brake pedal arm such that the plunger is depressed de-actuating the switch; and, upon user movement of the brake pedal arm, the switch plunger is permitted to extend and cause actuation of the switch contacts for energizing the vehicle stop lamps or brake lights.
During a typical automotive vehicle assembly in high volume mass production, the stop lamp switch is installed on a mounting bracket and moveably positioned thereon until the switch plunger contacts the brake pedal arm in its at-rest position against a travel-limiting stop or pad; and, the plunger is depressed sufficiently to de-actuate the internal switch contacts. The stop lamp switch is then secured in this adjusted position with the brake pedal at rest against its stop or limit pad. This technique of installation and adjustment has employed for known stop lamp arrangements, such as that shown and described in U.S. Pat. No. 5,162,625 issued in the name of John Comerford which describes a stop lamp switch having annular ribs on the plunger frictionally engaged by a clip provided in the actuator for adjusting the length of the plunger/actuator combination for initially positioning the de-actuated switch with respect to a brake pedal arm.
However, in the process of installing and adjusting the switch of the aforesaid known ribbed plunger, the initial contact of the plunger with the brake arm causes the plunger to depress the actuator to the limit of its travel, or bottomed-out position with respect to the switch casing before the plunger is ratcheted to its adjusted position where it is maintained when the switch is secured on its mounting. With the switch actuator at the limit of its travel, in the aforesaid known switch construction, it is not possible for the switch to subsequently absorb any overtravel of the plunger.
This has caused problems in service for plunger actuated switches employed in automotive brake light applications where the at-rest position of the brake pedal arm changes over the life of the vehicle by virtue of changes in the pad employed for the limit stop of the brake arm for the at-rest position. This can occur where the limit stop is an elastomeric pad which undergoes compression setting over a period of time under the load of the return spring for the brake pedal arm.
Furthermore, in the event that the brake pedal arm is moved against its limit stop pad by additional forces, as for example the vehicle operator pulling up on the brake pedal arm, the brake light switch plunger/actuator undergoes additional adjustment movement: this additional movement changes the at-rest position of the switch actuator with respect to the internal contacts and thus alters the point of switch actuation with respect to the brake pedal arm and may result in the brake lights not being de-energized in the pedal arm at-rest position.
Accordingly, it has been desired to provide a plunger actuated switch which may be installed against a user moveable operating member and adjusted in one operation at the time of installation with the plunger depressed in the at-rest position of the user operating member with the internal actuator of the switch at its travel limit and yet which is capable of thereafter absorbing overtravel from the at-rest position.